Leonard Steakcharmer is a shady gambler who is of some importance in The Mole, the Mob, and the Meatball.
Leonard usually hangs around at Ted E. Bear's Mafia Free Playland and Casino, where he has managed to amass 10 million tokens by cheating at Indian Poker when the Freelance Police encounter him. After they cheat him out of his 10 million, he steals the casino's famed Meatball Sandwich. Sam and Max capture him when they find him trying to sell the sandwich to Jimmy Two-Teeth and torture him with Your Mamma Jokes.
Afterward they keep him locked up in the closet as a souvenir. In What's new, Beelzebub? it turns out that has died and gone to hell while locked up, with his personal hell consisting of continuing to be locked up in the closet in a close replica of the office. Sam & Max manage to bring him back from the dead and appear to have released him, as he shows up as a guest at Sybil and Abe's wedding, with duct tape still over his mouth from his imprisonment.
Leonard Steakcharmer looks very much like Boris Krinkle from Telltale Texas Hold'Em, a joke on the fact that Krinkle is described as having an ill-fitting name, "more like a Leonard Steakcharmer." On the other hand, Steakcharmer is told he looks more like a Boris Krinkle.